USB not enumerating without JLinkExe running

RE: USB not enumerating without JLinkExe running

jeremysf — Tue, 28 Aug 2018 05:53:24 GMT

Good question, and now I feel dumb for not trying that!!

So, as it turns out I do not see these issues with the usbc_cdc_acm example in SDK 15.1. I am able to successfully plug/un-plug the USB cable (through a hub, without a hub, through two hubs) and the Mac enumerates my custom board as a /dev/tty.usbmodem**** regardless of if JLinkExe is connected or not. Yay, it's not the hardware!

Next, I tried the usbd_ble_uart sample with the same (working) results. Hub or no hub, JLinkExe or not, it works! Also, shedding further light onto the issue, the USB enumeration is *instant*. In the best case scenario with my app, the enumeration takes maybe two seconds, worst case (no hub, no JLinkExe) it takes like 7 seconds.

My app is refreshing an OLED screen via ~8MHz SPI on a timer interrupt. When I boosted the priority of the USBD above the SPI (i.e. to a lower number than the SPI code) everything started working reliably.

Sigh :)

Thanks for the advice!

RE: USB not enumerating without JLinkExe running

Sigurd — Mon, 27 Aug 2018 12:35:24 GMT

Hi,

The device answers some of the USB transactions, so it could be some timing issues with your application.

Do you see the same behavior if you test the unmodified usbd_cdc_acm example in SDK 15.1?

RE: USB not enumerating without JLinkExe running

jeremysf — Sat, 25 Aug 2018 05:42:42 GMT

I bodged another 4.7uF decoupling cap onto VBUS just in case, but no change. I also found if I plug my device directly into a USBC port (via a USBC->USB3 "adaptor") then I am able to get the USB to enumerate after 7s or so. If I go through a USBC->USB3 hub, it will never enumerate unless I am connected via JLinkExe. If I am connected via JLinkExe, enumeration happens in about 1s, regardless of through a hub or direct to the MacBook Pro USBC.

RE: USB not enumerating without JLinkExe running

jeremysf — Sat, 25 Aug 2018 03:19:36 GMT

So I hooked up my Packet-Master USB500AG and grabbed the traffic between the Mac and the device. Here's what the capture for a failed enumeration looks like. Firstly, I have filtered out all the NAK packets, to make it easier to see the big picture.

Below you can see the "Get Device Descriptor" never completes. The setup is ACK'd by the nRF52840, but then all attempts by the host to continue with the control transfer fail with NAK:

Now zooming in on the "Get Device Descriptor" transaction with NAKs (which repeat on in the thousands, interrupted with some SOFs):

For completeness, this is what it's like when the JLinkExe is connected. Here we can see successful enumeration. I can plug/unplug and re-trigger this enumeration as long as JLinkExe is running. If I quit the JLinkExe software (leaving the J-Link Pro connected to SWD), enumeration will fail...until I re-run and type "connect" in JLinkExe in which case, enumeration will succeed:

RE: USB not enumerating without JLinkExe running

jeremysf — Sat, 25 Aug 2018 01:23:33 GMT

So my custom board has an OLED screen. I am printing out status to it, and I can see that when JLinkExe is not connected, and my device fails to enumerate USB, it is still getting all the way to the 'APP_USBD_EVT_POWER_READY' event in my usbd_user_ev_handler() despite failing to enumerate. I correctly see 'APP_USBD_EVT_POWER_REMOVED' through 'APP_USBD_EVT_POWER_READY' events when I unplug and plug back in the USB cable, but no device enumeration (i.e. /dev/tty.usbmodem*** does not show up)...until...I connect again with JLinkExe, then I get device enumeration.

In the working case, the last event I get after successful enumeration is "APP_USBD_EVT_DRV_RESET".

In the case where JLinkExe is disconnected (and it fails to enumerate), I alternate between getting "APP_USBD_EVT_DRV_SUSPEND" and "APP_USBD_EVT_DRV_RESUME" events but never get to the "APP_USBD_EVT_DRV_RESET" state.

RE: USB not enumerating without JLinkExe running

jeremysf — Fri, 24 Aug 2018 21:11:21 GMT

I just upgraded to SoftDevice 140v6.1 and SDK 15.1 and redid my sdk_config.h and Makefile from scratch using a blend of buttonless_dfu, ble_hrs and usb_cdc configs.

Sadly, no change in behavior. Works great if JLinkExe is actively "connected", no enumeration if JLinkExe is disconnected. As soon as I re-connect JLinkExe, within a few seconds, USB gets enumerated by my Mac.